This proposal will investigate the expression of human antibody V genes in health and autoimmune disease. Although much has been learned in recent years concerning the molecular mechanisms governing the generation of antibody diversity, the relationship(s) between the factors responsible for diverse V-gene expression and autoimmunity is not clear. Do pathologic self-reactive antibodies arise form enhanced or constitutive V gene hypermutation or do they result from genetic deficiencies in the inherited gene-line genes? This investigation will take advantage of recent technological advances to explore these issues. Using synthetic peptide corresponding to conserved variable region framework or complementary determining regions of human antibodies, we will elicit murine monoclonal antibodies and rabbit antisera for use as molecular probes in the investigation of V gene expression of serum and surfact immunoglobulin. The latter will use multiparameter analyses in flow cytometry performed on blood and marrow lymphoid populations from normal individuals, patients with rheumatoid arthritis and recipients of allogeneic marrow transplants. These studies will investigate for differential expression of selected V gene subgroups, major cross reactive idiotypes associated with autoantibodies, and germ-line encoded variable region framework determinants. In addition, we will use human hybridomas and B lymphoblastoid lines as an in vitro system to study the stability of human isotype and V gene expression, the relationship between isotype switching and V gene somatic mutation, the association of rheumatoid factor activity with major cross reactive idiotypic determinants. Finally, we will investigate for single stranded DNA breaks in specific genes and explore the relationship between such chemical changes and the relative mutation rates in immunoglobulin genes. Through such studies we may gain a greater appreciation of factors controlling human antibody diversity and insight into host factors that may predispose one to autoimmune disease.